1. Field of the Invention
This invention relates to a biochemical process and, in particular, relates to a method and enabling apparatus for control of an aerobic biochemical process.
2. Brief Statement of the Prior Art
There are a substantial number of biochemical processes which utilize bacteria, fungi, molds or actinomycetes for the industrial fermentation of wastes to innocuous or desired end products. Some of these processes include the bacterial production of proteins from hydrocarbons, vinegar from alcohol, citric acid from sucrose, and the disposal of industrial and municipal wastes by aerobic decomposition, typically with the activated sludge process. Representative of industrial wastes which are treated in this fashion are wastes of textile plants, rubber plants, canneries, dairies, meat packing plants, pulp and paper plants, etc.
All of the aforementioned biochemical processes, whether conducted batch-wise or continuously, require the admixing of a microbial food with a microbial culture which is in a food limited growth phase and contacting the mixture in a holding tank or vessel with a supply of oxygen to insure the rapid growth of the microorganism.
Commonly, the microbial culture utilized in the process is substantially depleted of a supply of microbial food and often is a recycle stream such as recycled sludge in an activated sludge process. This recycle of the aqueous microbial culture is usually performed at a constant weight or volume proportion to the incoming raw microbial food medium. A difficulty which is frequently encountered is that the recycled microbial culture is not of uniform and consistent activity. Thus, if the aqueous material being processed contains any inhibitors of microbial action, e.g., dissolved heavy metals or toxins, the microbial culture can have substantially lesser activity than expected and, accordingly, when recycled at a constant volume or weight mass, there results an inadequate innoculation of the incoming stream to insure its rapid and complete aerobic decomposition. A similar result occurs if the composition or concentration of microbial food in the aqueous microbial food medium changes materially.
Because biochemical processes are conducted in relatively dilute aqueous media and require substantial reaction times, there is a substantial time lag in the detection of any inhibition of activity of the recycle microbial culture or in the composition of the incoming microbial food medium. As a result, upsets in the process, particularly when conducted in a continuous fashion, have substantial and detrimental consequences in the operation.